AP Photo/Seth Perlman, File People line up to vote in the primary at a precinct in Bradfordton, Illinois. W hen Donald Trump describes next Tuesday’s election as “rigged,” he conflates two things. The first is that “the establishment,” in whatever form, is powerfully arrayed against ordinary Americans and against Trump himself as their tribune. The second, darker and more dangerous, allegation is that the voting process itself cannot be trusted, that even if people come out and vote for him, “massive” voting fraud on Election Day and the manipulation of the count will steal the election from him. The first, though Trump is hardly the best messenger for it, is at least an arguable proposition, and has some resonance in the progressive critique. Trump’s second charge, however, poses a serious threat to our democracy and is an essential tool of authoritarian-leaning demagogues. Just as important: It really can’t happen here. We need to be clear about that, and we also need to be clear...